Is it permissible to give money from a vow (nadhr) to a poor woman who has unemployed children so that she may buy an Eid sacrifice with it?

Undertaking a vow is disliked, but whoever vows obedience to Allah must fulfill it. A vow is for whomever the one making the vow specifies. If no specific recipient is designated, then it is permissible to spend it on any act of righteousness, and the one fulfilling the vow should seek out the most needy. Therefore, there is no impediment to giving to the aforementioned woman from the vow if it was not specifically designated for others, especially if she is in need. Her merely selling vegetables does not prevent giving to her.